Beltz was first named in the Burras squad in 2016. That year he played in the 2016 Junior Oceania Cup in Gold Coast, Queensland, Australia and a qualifier for the 2016 Men's Hockey Junior World Cup.[5]
After gaining qualification for the Junior World Cup, Beltz was also an inclusion in that team, where Australia lost 3–0 to Germany in the Bronze Medal Match to finish fourth overall.[6]
Beltz made his international debut for the Australia national team, the Kookaburras, in 2015, in a test match against India.[7]
Since his debut, Beltz has been a regular inclusion in the Kookaburras squad, most notably winning a gold medal at the 2016 Men's Hockey Champions Trophy in London, England, United Kingdom.[8]
In November 2018, Beltz was named in the Kookaburras squad for the 2019 calendar year.[9][10]
In 2022, Beltz helped Australia to gold at the 2022 Commonwealth Games in Birmingham, England, United Kingdom, defeating India 7–0 in the final.[11]
Beltz was selected in the Kookaburras squad for the delayed 2020 Summer Olympics in Tokyo, Japan. In the group stage, Beltz scored in Australia's 7–1 win against India.[12] The team reached the final for the first time since 2004 but couldn't achieve gold as they were beaten by Belgium in a shootout.[13]
